This invention relates to rotary internal combustion engines of the trochoidal type, and more particularly to a means of preventing entry of exhaust gases into the intake channel during idling or operating at low load.
In such engines the intake channel has an orifice controlled by the rotor, at the inner surface of the engine housing. There is in such engines a certain amount of overlap between intake and exhaust ports after the opening of the intake port to a given chamber and before the exhaust port closes to that chamber, and during idling or operation at low load the underpressure caused by the enlargement of the intaking chamber may cause the intake channel to become filled with exhaust gas. Even though the throttle flap may be positioned as closely as possible to the orifice of the intake channel, for constructional reasons the axle of the flap must be positioned at least far enough back from the opening that at the fully opened condition the edge of the flap will not protrude into the operating chamber. The filling of a portion of the intake channel with exhaust gas has the result, particularly when idling or operating at low load, that the fresh gas entering into the intaking operating chamber encounters a sizable body of exhaust which may impair the formation of an ignitible mixture.
It has also been found that with trochoidal rotary engines of the prior art it is more difficult to produce a good fuel-air mixture in the intake channel than with reciprocating piston engines. In reciprocating engines the hot intake valve makes a substantial contribution to preparing the mixture by vaporizing such droplets of fuel as may be still liquid. In the rotary engine the intake zone is never exposed to combustion, and hence has no such hot members to aid in vaporization.
There is known a carburetor in which, in the channel leading to the intake manifold, instead of a throttle flap there is disposed a slide member movable longitudinally of the mixture flow, having a portion with a conical surface cooperating with a mating conical countersurface and forming an annular throttling gap therewith. When the gap is small, depending on the load condition, the fresh gas flows through at high speed and tiny droplets of liquid fuel are thoroughly atomized. With such a design, however, because of its arrangement, there necessarily exists a relatively large volume in the intake pipe between this throttling device and the intake port, which causes the same difficulty as described above, at idling or partial load. Further, the device is limited to carburetors and cannot be used for supplying fuel by injection.
Other expedients have been tried to prevent entry of exhaust gas into the intake channel, such as rotary valves or flap valves therein. The rotary valve must be positioned even further back from the orifice than an ordinary throttle flap, since there must be enough metal to constitute the barrel for rotation of the valve therein. Flap valves of the reed type are not sufficiently reliable; they may be too stiff to close fully, or they may impede inflow of fresh gas.
The throttle valving arrangement of this invention overcomes these limitations of the prior art.